Effect of Cr6 on growth, serem electrolytes and some hormone activities in Cyprinus carpio

The Cyprinus carpio （6 months old） were exposed to water bodies with different concentration of Cr^6＋ ranged from 0,0.12, 0.67,1.22, 3.66, 10.97 and 32.91 mg?L^-1, respectively. An increase in growth rote （AGR and ALR） was observed in T0.12 to T3.66 Cr^6＋ -treated groups. The results showed that Cr^6＋ also affected serum osmolarity and serum electrolytes. The serum osmolality and Na^＋ and Ca^2＋ concentration were significantly higher in the Cr^6＋ - treared groups than in the controls. Increase of serum K^＋ was also observed, but it was only significant in T10.97 group. The concentrations of serum Mg^2＋ from a few Cr^6＋ treated groups were decreased. No obvious serum Cl^- concentration changes were observed. Cr^6＋ affected serum hormonal responses. The T3 content in T3.66 group and T4 content in T10.93 group, and the cortisol levels from all the groups treated with Cr^6＋ concentration 0.67 and higher were significantly increased. The nutritional contents （crude protein and crude fat） in fish from most of the Cr^6＋ treated groups were lower than the control. The concentration of Cr in a fish body treated with Cr^6＋ had a distribution pattern： muscle 〈 gill 〈 liver 〈 Intestines. The Cr concentration in fish muscle from group T32 91 （3.00 mg?kg^-1） and the Cr concentration in intestines from group T0.67（2.24 mg?kg^-1 ） and from all the groups treated with higher Cr^6＋ exceeded the national maximum limit for food safety.